1. Field of the Invention
The present invention pertains to a method for driving a plasma display panel (hereinafter referred to as ‘PDP’).
2. Description of the Related Art
As one type of PDPs operated on a matrix display method, a discharge-type alternating current PDP has been put to practical use, and various constructions and driving methods have been proposed therefor.
A discharge-type alternating current PDP includes a plurality of column electrodes (address electrodes) and a plurality of row electrode pairs that extend perpendicular to these column electrodes. Each of the row electrode pairs forms one display line. The row electrode pairs and column electrodes are covered by a dielectric layer and are separated from the discharge space. A discharge cell is formed at an intersection of each pair of row electrodes and each column electrode. These discharge cells are infused with a discharge gas such as xenon (Xe).
In order to display a color image, each pixel of the PDP emits light in the three primary colors of R (red), G (green) and B (blue). Specifically, as illustrated in FIG. 1 of the accompanying drawings, each pixel P of the PDP includes a red discharge cell CR that emits red light (R), a green discharge cell CG that emits green light (G), and a blue discharge cell CB that emits blue light (B). Each discharge cell has a fluorescent layer that corresponds to the color of the light emitted by that discharge cell.
In order to display an image corresponding to image signals input to the pixels, gradation driving of the PDP is carried out using a sub-field scheme or method. Sub-field methods include the selective erasing address method and the selective writing address method. In the selective erasing address method, a wall charge is formed beforehand in all discharge cells by a reset discharge induced upon simultaneous application of a reset pulse to both row electrodes in each row electrode pair (simultaneous or global reset operation), the wall charge in the discharge cells is selectively erased in accordance with input image signals (pixel data writing operation), the discharge cells are caused to emit light in accordance with the wall charge remaining in the discharge cells due to a sustaining discharge triggered by the alternating application of sustaining pulses to the row electrodes of the row electrode pair (light emission sustaining operation), and the above operations are repeated. In the selective writing address method, on the other hand, the wall charge is erased in all the discharge cells beforehand by the reset discharge caused upon the simultaneous application of a reset pulse to both row electrodes in each row electrode pair (simultaneous reset operation), a wall charge is formed in selected discharge cells in accordance with input image signals (pixel data writing operation), the discharge cells are caused to emit light in accordance with the wall charge formed in the discharge cells upon the sustaining discharge triggered by the alternating application of sustaining pulses to the row electrodes of the row electrode pair (light emission sustaining operation), and the above operations are repeated.
In both driving methods, although the pulse voltage (V) of the pulses supplied simultaneously to the two row electrodes of the row electrode pair in the simultaneous reset operation is identical for both pulses, the pulses have different (opposite) polarities. Accordingly, when the difference in electric potential between the row electrodes exceeds the discharge start voltage, electric discharge occurs between the row electrodes.
For example, when ‘red’ is being displayed by the pixel P, discharge occurs repeatedly between the pair of row electrodes in the red discharge cell CR during the light emission sustaining operation, thereby causing the red color to be emitted (displayed), and the discharge start voltage is maintained at a high level between the address electrode and the row electrodes. However, because no discharge occurs in the green discharge cell CG and the blue discharge cell CB in the same pixel, the discharge start voltage between the address electrode and the row electrodes becomes low.
Therefore, when a reset pulse is applied to the row electrodes in all discharge cells in the subsequent simultaneous reset operation, a discharge may occur between address electrode and row electrodes for the green and blue discharge cells CG and CB because the discharge start voltage between the address electrode and the row electrodes for the green and blue discharge cells CG and CB is low. Because the discharge occurring between the address electrode and the row electrodes for the green and blue discharge cells CG and CB has a higher light intensity than the discharge occurring between the address electrode and the row electrodes for the red discharge cell CR having a higher discharge start voltage, the uniformity among the light emission intensities of the three primary colors in the pixel is destroyed, and a photogene (afterimage, ghost image) of a complementary color appears after ‘red’ is sometimes perceived (displayed).
When a plurality of reset pulses are applied to the row electrode pairs in the simultaneous reset operation, an amount of wall charge in the vicinity of the address electrode and the row electrodes increases if the first discharge between the address and row electrodes is strong. This triggers a strong discharge between the address and row electrodes upon application of the second and third reset pulses to the row electrode pairs. As a result, the photogene of a complementary color sometimes appears after ‘red’ is displayed.
The above tendency becomes particularly significant when display is alternated from ‘red’ to ‘black’. The tendency for a luminance photogene to appear is marked in a PDP if the discharge gas in the PDP has a high concentration of xenon gas and the discharge start voltage between the address and row electrodes is relatively low in the original setting of the PDP.